1. Field of the Invention
The present invention relates to a driving apparatus for driving a plasma display panel employing a matrix display scheme.
2. Description of Related Art
In recent years, display units with a screen increased in size have longed for thin display devices. AC (Alternating current discharge) plasma display panels have received attention as one of the thin shape self-light-emitting display devices.
A discharge cell corresponding to one pixel in a plasma display panel is adapted to use a discharge phenomenon to perform light-emission display and thus have only two states, xe2x80x9clight-emittingxe2x80x9d and xe2x80x9cnon-light-emittingxe2x80x9d. In order to implement the display of gray scale brightness in accordance with a video signal, the plasma display panel is driven by a sub-field method.
In the sub-field method, one field period is divided into N sub-fields. A number of times of light emission corresponding to a weight of each bit digit of pixel data (N-bit data obtained by sampling a video signal corresponding to each pixel) is assigned to each sub-field. Here, first, in accordance with the aforementioned pixel data, sub-fields allowed to emit light and those not allowed to emit light are determined. Then, of these N sub-fields, only in the sub-fields allowed to emit light, discharge is generated for the number of times of light emission assigned to the sub-fields.
For example, as shown in FIG. 1, in a case where one field period is divided into four sub-fields SF1-SF4, a number of times of light emission are assigned to each of the sub-fields SF1-SF4 as follows. That is,
SF1: 1
SF2: 2
SF3: 4
SF4: 8.
Here, one visually identifies display brightness xe2x80x9c3xe2x80x9d when discharge is generated only in the sub-fields SF1 and SF2, and display brightness xe2x80x9c7xe2x80x9d when discharge is generated in the sub-fields SF1-SF3.
FIG. 2 is a view showing the configuration of a plasma display device, driven by such sub-field method, for displaying images.
As shown in FIG. 2, such plasma display device comprises a plasma display panel 10 (hereinafter referred to as xe2x80x9cPDP 10xe2x80x9d) and a drive portion for driving the PDP 10 in accordance with an input video signal.
The PDP 10 comprises address electrodes or m column electrodes D1-Dm, and n row electrodes X1-Xn and n row electrodes Y1-Yn, the row electrodes being arranged in transverse relation with each of the column electrodes. Here, a pair of a row electrode X and a row electrode Y forms a row electrode that corresponds to one row of the PDP 10. The column electrodes D and the row electrodes X and Y are dielectrically insulated in discharge spaces, and a discharge cell is formed corresponding to one pixel at a crossover of each of the pairs of row electrodes and a column electrode.
However, in the configuration shown in FIG. 2, there is a problem that the spectrum of radiation noises that are generated by a variety of pulses for driving the display panel 10 concentrate on the natural frequency derived from the drive clock signal, thus increasing the radiation noises.
The present invention has been developed to solve the aforementioned problem. An object of the present invention is to provide a driving apparatus for driving a plasma display panel that can reduce radiation noises.
The driving apparatus for driving a plasma display panel according to the present invention drives a plasma display panel in which a plurality of row electrodes and column electrodes define discharge cells at their respective crossovers. Each of the plurality of row electrodes is arranged for each of scan lines, and the plurality of column electrodes are arranged in transverse relation with said row electrodes. The unit comprises panel drive means for applying a predetermined drive pulse repeatedly to each of said row and column electrodes in accordance with an input video signal. The unit also comprises application timing varying means for varying the application timing of said drive pulse as time goes by.